Vibration isolating mounts



Feb. 10, 1959 R. G. HARTENSTEIN ET AL 87 VIBRATION ISOLATING MOUNTSFiled Jan. 23, 1956 2 Sheecs-Sheec 2 Fig. I2. Outpt Withouf BumpersIn;put 01 Resonance /Output With Bumpers l Force United States Patent OVIBRATION ISOLATING MOUNTS Claims. (C1. 267-1) This invention relates toan article of manufacture adapted for use in damping transmission ofvibration and shock between two bodies.

In a copending application Serial N0. 554,889, filed December 22, 1955,and assigned to the assignee of the present applicati0n, there isdescribed a novel type of vibration isolation mount which is eapable ofisolating shocl; and vibration in three planes. That mount comprises,essentially, a plurality of flexible cables embedded in a sheet ofelastic material, such as rubber 01 plastic. The opposite ends of theaforesaid cables are attached to the members which are to be isolated ina manner such that the assembly forms a quadrant cf a cylinder (i. e. itmakes a right angle bend).

Although the mount shown and described in the afore said applicationSerial N0. 554,889, will perform satisfactorily for its intendedpurpose, it was found to be impractical to a certain extent because ofcertain inherent structural limitations. One of these limitations wasdue 10 the fact-that the aforesaid elastic sheets Were fastened tothebodies to be isolated byfriction screws or other similar fasteningmeans. Since the elastic sheet would yield under the pressure of thefriction screws when t ightened it would permit the screws to loosenWhen the assembly was subjected to vibration; and, thus, the screwshadio be tightened from time to time.

Accordingly, it is an object of this invention to provide a new andimproved mount capable of isolating shoek and vibration in all threelanes and suitable for practical commercial purposes.

Another object of the invention lies in the provision of a vibration andshock isolating mount which is economical in size and weight for a givenloading condition. Due to the bending moment of a mount 0f the typedescribed above, it is desirable to keep the mount thin at the middleand at its extreme edges for high frequency vibrations, while it isdesirable to make the mount thicker at the edges to restrain motion atresonance. The variation in thickness should be gradual to keep stressconcentrations at a minimum under shock loading conditions. As willbecome apparent from the follovving description, these desirablecharacteristics are combined in the mount of the present invention byemploying projections which extend -outwardly over the edges of theelastic sheet of the mount.

Other objects and features of the invention will becorne apparent fromthe following detailed description taken in connection with theaccompanying drawings which form a part cf this specification and inwhich:

Fig. 1 is a view illustrating a typical assernbly employ ing the shockand vibration isolator of the invention;

Fig. 2 is a view of the comb attachment for the mount shown in Fig. l;

Fig. 3 is a view illustrating the cable construction of the mount;

Fig. 4 illustrates the method of fabricating the mount of the invention;

Fig. 5 graphically illustrates the bending moments produced in theisolator mount;

Figs. 6 through 11 illustrate Various embodiments 0f the bumperattachment for the mount, said bumper being used to greatly improve thecharacteristics of the mount over a wide range of frequencies; and

Fig. 12 is a graphic illustration of the performance of the mount withthe bumpers added.

Referring to Fig. 1, the assembly shown comprises a platform 10 on whichare mounted Weights 11 which represent electronic er other equipment.The platform 10 is connected to, a chassis 13 through two vibrationisolation mounts 12 and 14. Bach cf these mounts comprises a series ofparallel flexible cables embedded in a sheet cf elastic material such asrubber, the mount being bent at its center to form a quadrant of acylinder. As is fully explained in copending application Serial N0.554,889, filed Decernber 22, 1955, the mounts give exceptionally goodVibration isolation in all three planes.

Cornponents of the improved Vibration and shock isolating mount of thepresent invention are shown in Figs. 2 and 3 and include a pair of combsupporting members 16 and 16'. The combs comprise elongated bars ofmetal er other suitable material in which are machined trans- Verseslots 18. A series of mounting holes 20 are provided in the comb tofacilitate fastening to the chassis 13 and the mounting plate 10.Extending through slots 18, and woven between the combs 16 and 16 (Fig.3), is a continuous flexible cable 22. The cable is wrapped around theends of the slots and is soldered to one or the other cf the combs atits ends 24 and 26. With this configuration, the combs obviously cannotpull apart.

As is shown in Fig. 4, two sheets 28 and 30 of rubber er other elasticmaterial are placed 011 the.top and bottom of cable 22 and arecernen-ted together 01' vulcanized under the pressure of dies 32 and 34.The resulting product is a sheet of elastic material embedded with thecontinuous flexible cable 22. The two combs 16 and 16' can thus befasten'ed securely to the bodies which are to be isolated(plate 10 andchassis 13) with the assurance that the screws 01' other elementsextending through holes 20 will not loosen under severe vibrations.

In Fig. 5, it can be seen that the bending moment of the mount increasesfrom a minimum at its center to a maximum at its outer edges. It isconceivable that a mount c0uld be manufactured having a cross-sectioncouforming to that of the bending moment to obtain a lightweight andeconomical structure. Such a mount would function satisfactorily at 10Wfrequencies where bending is experienced, but the mount would be quitenoisy at high frequencies due to its non-uniform cross-section. T0facilitate the high bending moments at the resonant frequency and lowbending moments at higher frequencies, the burnper attachment shown inFigs. 611 was developed. In Fig. 6 the burnper comprises an elongatedelastic projection 36 which extends out over the surface of the isolatorin combination with a metal plate 38 which, together With bolts orrivets 40, holds the comb 16 and projection 36 against the plate 10 orchassis 13. In Fig. 7 a second, shorter projection cf elastic material41 is included with a longer elastic projection 39 to give the structureadded strength. In Fig. 8, theprojection comprises a sheet of metal 42having its outer edge bent to form a lip 44. A sheet cf elastic material46 is combined with the lip configuration in Fig. 9. In Fig. 10 the lip48 is an integral part of the comb 16 or 16', and in Fig. 11 a sheet ofelastic material 50 is placed Underneath the lip 48. Other and furtherconfigurations may, 0f c0urse, be used depending upon requirernents. The

configuration which is most suitable for a particular application maybest be determined by expen'ment.

At high frequencies (above resonance) there is no intitnate shearcontact betwen the elastic sheet of the mount and the bumpers.Consequently, the eflective thickness of the sheet at these higherfrequencies is kept constant. At the resonant frequemcy and Lindershock, bendi'ng3tarts in the isolator. Tlieisoltor irr'rmediatelyintercep ts the bumper which (1) changes the fundamehtal fi-equency cfthe mount, (2) physically restrai'ns the motion of the mount, (3)absbrbs energy due to friiztion between the mount and bum1aer, and (4)eliminates'stress concentrations at the ends of'tl1e isolator. Inaddition, forces Transmitted through the mount are greatly reduced bythe ad-dition of the 'bun1pm's as shown in Fig. 12. All cf this isaccomplished without introducing 'any high frequeney noise of any kindin any plane.

The present invention thus prvides an improved, economical vibratiou andshock isolating mount which is capable of isolating Vibration and shockin all three lanes.

Although the invention has been described in connection with certainspecific embodiments, it should' be readily apparent to those skilled inthe art that various changes, in forrn and arrangem ent cf parts can bemade to suit requirements without departing frorn the spirit and scopeof the invention.

We clai-m as our inventi0n:

l. An article cf manufacture adapted for use in damping transmission 0fvibration and shdck between two bodies and c0mprising a pair of parallelelongated members each having a series of spaced projections an one facethereof, a continuous cable Wrapped around' said projectiom and wovenbetween said members, elastic material surrounding said cables to forrna composite elastic sheet embedcled Witl1 woven zahle, means f0rsecuring each of said members to an associatecl one' of said bodies, andprojections extending from said inembers outwardly over the surface ofsaid elastic sheet. 1

2. An article 0f manufacture adapted for 1 1se in damping transmissionof vibration and Shock b'etween two bodies and comprising a pair ofelongated members each having a series 0f slots formed thereinperp'endicular to the long transverse dimension of said members, acontinuous flexible metal element wrapped around said slots and w0venbetween said members, elastic material surrounding said element to forma composite elastic sheet em'beclded with said wuven element, andprojections extending from said member outwardly over the surfce of saidelastic sheet.

3. An article of manufacture adapted for use in damping transrnission ofvibration and shock b'etween two bodies and comprising a pair ofparallel elongated members each having a series of s paced projectionson one face thereof, a continuous flexible element wrapped around saidprojeetions and woven between said members, elastic material surroundingsaid element to form a ccvm' p0site elastic sheet embedded With saidwoven element, and projecti0ns extending from said'rnembers outwardlyover the surface of said elastic sheet.

4. An article 0f manufacture adapted for use in damping transmission cfvibration and shock from one body to another and comprising a pair ofparallel elongated rnembers, projections on said rnembers, a continuousflexible element woven between said projections, elastic materialsurr0unding said element to form a. composite elastic sheet ernbeddedwith said woven element, and projections extending from said menrbersoutwardly over the surface cf said elastic sheet.

5. An article of manufacture adapted for use in damp= ing transmissionof vibration and shock from one body to another and -comprising a pairof parallel elongated References Cited in the file of this patent UNITEDSTATES PATENTS 1483561 Ungar Feb. 12 1924 1619457 Bell Mar. 1, 19271671764 Dickey May 29, 1928 1709,207 Garnmeter Apr. 16, 1929 2139,840McCone Dec. 13, 1938 2578885 Huff Dec. 18, 1951 2643,529 Thomas Inne 30,1953

